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root (Barberon et al.
2008
; Yoshimoto et al.
2007
). The high-affinity sulfate trans-
porters are very well studied. In
Arabidopsis thaliana
they comprise three genes
(SULTR1;1-3) and belong to the clade which forms Group 1 of the sulfate trans-
porters (Fig.
3.2
). The primary sulfate acquisition in roots is mediated by two
transporters: SULTR1;1 and SULTR1;2 (Fig.
3.1
). Various studies confirmed the
expression of these two genes in root hairs, root epidermal and cortical cells (Rae
and Smith
2002
; Takahashi et al.
2000
; Yoshimoto et al.
2002
) suggesting the
capacity of these tissues for a high-affinity sulfate influx into the symplast.
SULTR1;3 appears to be an exception in this group with specificity of localisation
to the phloem in both roots and cotyledons (Yoshimoto et al.
2003
). Sulfur
Fig. 3.1 Sulfate transport system in
Arabidopsis thaliana. Blue
shapes and labels indicate sulfate
transporters (SULTRs) mediating transport across plasma membranes.
Dashed arrows
indicate yet
unknown transport pathways